The present invention generally relates to the field of X-ray radiography system, and particularly relates to a rotation mechanism for an x-ray wallstand housing, an x-ray wallstand housing and a radiography system using the same.
X-ray radiography systems existing in the current market are mainly divided into economical-type and non-economical-type radiography systems according to the cost. For a radiography housing of an 0economical-type system, it is generally of fixed type with simple structure, it has no rotation movement and only can perform up-and-down movement, and it is mainly used for taking chest radiograph. According to imaging medium, X-ray radiography systems are mainly divided into three types, i.e. film radiography system, CR (Computerized Radiography, X-ray Computerized Radiography) radiography system and DR (Digital Radiography, X-ray Computerized Radiography) radiography system. CR radiography system is a transitional system between film and digital-medium.
The most widely used radiography system in clinic at present is DR radiography system, which can realize multiple functions on a single system. That is, it is required not only being capable of making up-and-down movement, but also having rotation function, i.e. being capable of shooting an image of e.g. a skull in tilting angle.
As an important component of a multi-function digital radiography system, for example, a chest radiograph stand, can move the radiography housing to different heights and positions for different application demands, and meanwhile can rotate the radiography housing to maintain it at any position of −20° to 90° with respect to a vertical plane.
As shown in FIG. 1, a typical x-ray wallstand housing is illustrated, in mechanical structure, which mainly includes a wallstand column 1, a carriage 2, a radiography housing 3 and a rotation mechanism. Wherein the carriage 2 is mounted on the wallstand column 1 and can make up-and-down movement in vertical direction; the rotation mechanism is positioned on the carriage 2 for driving the radiography housing 3 to position it at any height and angle. In addition, the rotation mechanism also can be integrated together with the carriage 2.
Further, as shown in FIG. 1, the rotation mechanism comprises a rotating shaft 4, a gas spring 5, a ball screw nut seat 7, a connecting rod 6, a ball screw base 12, a brake 16, a clutch 14, a conveyor belt 15, a ball screw 17 and a motor 8, said motor 8 drives said clutch 14 through conveyance by said conveyor belt 15, said clutch 14 is connected with said ball screw 17, said ball screw 17 is connected with said ball screw base 12 and said ball screw nut seat 7, said connecting rod 6 is in parallel with said gas spring 5 and is connected with said ball screw nut seat 7, said brake 16 is positioned on one end of said ball screw 17. The rotation mechanism is mainly used for realizing rotation movement of the radiography housing 3, the support on the rotation mechanism is connected to a rotating bending plate 18, whereby it acts on the rotating bending plate 18, such that the radiography housing 3 fixed on the rotating bending plate 18 rotates about the rotating shaft 4. The gas spring 5 and the upper end of the connecting rod 6 is connected with the upper support of the rotation mechanism in a hinge joint way.
The lower end of the gas spring 5 is connected to the lower support fixed at the rotation mechanism base in a hinge joint way to form two-force bar structure. The gas spring 5 is always used for balancing gravitational torque generated by the weight of the radiography housing 3, the gas spring 5 is similar to a spring, it is compressed when subjected to an external force, and it extends outwards when the external force is reduced to a level at which it is unable to balance the extending force of the gas spring. The variation of the length of the gas spring maintains consistent with the rotating angle of the radiography housing 3, the arm of force of the gas spring (the distance to the rotating shaft center in the direction of the support force) varies with the angle, so the variation of the torque of the support force of the gas spring 5 with the angle can be used to simulate the variation of the gravitational torque of the radiography housing 3 with the angle to achieve an approximately balancing effect. When the radiography housing 3 is rotated closing to 90°, the gravitational torque of the radiography housing 3 gradually draws close to 0 with the variation of the angle, the torque of the support force of the gas spring 5 is also reduced to a minimal value (greater than 0), thus when the radiography housing 3 is rotated closing to 90°, the torque of the support force of the gas spring 5 is greater than the gravitational torque, such that a surplus balancing torque is formed to be an external force rotating the radiography housing 3.
The lower end of the connecting rod 6 is connected with the screw nut seat 7 in a hinge joint way for conveying electrical and manual operation force to realize rotation of the radiography housing 3. The length of the connecting rod 6 maintains the same, the lower end thereof moves horizontally with the screw nut seat 7, the upper end thereof acts on the upper support, makes rotation movement about the rotating shaft 4 together with the radiography housing 3. The torque of the connecting rod 6 varies with the variation of the force applied on the connecting rod 6 and the arm of force thereof (the distance from the axis line of the connecting rod to the rotating axis center).
In FIG. 1 a motor 8 is also comprised which can drive the rotation mechanism to rotate, specifically, it drives the radiography housing 3 to any position and angle through the ball screw nut seat 7 and the connecting rod 6. In addition, the clutch 14 positioned between the motor 8 and the ball screw nut seat 7 can realize manual operation upon the radiography housing 3. The motor 8 is a drive source. The ball screw 17 is of high lead, when it is in free-rotation state, it not only is used for conveying driving force from the motor 8, but also can drive the ball screw 17 through the ball screw nut seat 7 to release force from the connecting rod 6, realizing manual operation. The brake 16 acts on the ball screw 17 and achieves the purpose of braking through the rotation and braking of the ball screw 17. The clutch 14 causes the electrical and manual operation to be respectively independent.
During electrical operation, an electrical button is pressed by hand, the clutch 14, the motor 8 and the brake 16 are simultaneously powered on, the clutch 14 suck, and the brake 16 disengages. The motor 8 rotating drives the ball screw 17 to rotate through the belt 15 and the clutch 14, to drive the ball screw nut to make linear movement, the ball screw nut drives the screw nut seat 7 to rotate the radiography housing 3 about the rotating shaft 4 through the connecting rod 6. The motor 8 is forward and/or reverse to realize the forward and/or reverse rotating direction of the radiography housing 3. During electrical operation, the surplus torque of the gas spring 5 is balanced through the connecting rod 6, electrical control is gradually started and gradually stopped, avoiding the possibility of the radiography housing 3 shooting over 90 degree.
During manual operation, an operator acts on the edge of the radiography housing 3 with one hand, presses a manual switch with the other hand, and assists the rotation movement of the radiography housing 3. When the manual switch is triggered, the motor 8 and the clutch 14 are powered off, the power-down brake 16 is powered on and disengages, the ball screw 17 is separated from the motor drive, the operation force of the operator is applied on the ball screw nut seat 7 through the connecting rod 6, the ball screw 17 of high lead is rotated, whereby manual operation can be realized.
However, when manual operation is performed on the radiography housing 3, the rotation mechanism would have the following problem:
As shown in FIG. 2, because the radiography housing 3 is symmetrical to the rotating shaft 4, in the rotating course of the radiography housing 3, the gravitational torque thereof conforms to the cosine curve. But in the whole course, the gas spring 5 neglects small linear variation in the force value, and simplifies it into constant force. When the radiography housing 3 rotates closing to 90 degree, since there is no force to balance the gas spring 5, the radiography housing 3 will generate a dropping force F. The faster the rotation movement is, the more obvious the dropping is. In other words, when the radiography housing 3 rotates from 0 degree to 90 degree, since the torque of the gas spring 5 exceeds the gravitational torque of the radiography housing 3 when the radiography housing 3 is close to 90 degree, the radiography housing 3 will drop at quick speed and shoot over 90 degree, this will stop under the rotary detent function of the radiography housing 3, the overly quick speed in addition with overshoot will bring about the risk of pinch.
How to solve the problem of drop of the radiography housing 3 during manual operation always troubles those skilled in the art.